Bussmann Auxiliary Fuse and Relay Module Installation

B00mb00m said:
what are you doing to for circuits / switches that you want on switched power?
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Super easy. Find a fuse in the glove box that is switched power. Put a fuse tap there, or splice into the circuit somewhere. Fuse to 2.5 amps or similar. From there, go to your switch. Then from the switch to the relay input in the RTMR/RFRM. Fused relay power is supplied through the RTMR/RFRM (with an appropriate fuse size for the load) to the load.
The relays themselves draw a very small amount of current. All 10 relays combined should draw less than an amp, so you can safely put up to 10 relay fed switches on one splice or fuse tap fused to 2 amps.
 
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Got a request for a more detailed parts list.

Here is what I ordered. I chose Waytek Wire for most of my items. Even though they have a minimum order number for many parts, it still works out to be a lot cheaper than buying fewer parts on Amazon or elsewhere.

Bussmann base:
The base RTMR or RFRM for your project. I chose the larger RFRM. All the quantities past this section assume you buy an RFRM. Adjust as needed for an RTMR.
Bussmann plugs and seals:
Used to seal empty cavities and around any cables entering the box. Different colors correspond to different wire gages.
Connectors:
These connectors are crimped onto wires and then snap into the back.of the Bussmann. They have slots that the fuse or relay will slide into. (QTY=50 for all.)
Fuses and relays for internal use:
Wire and wiring accessories
(No links provided. Buy any marine grade oxygen-free copper stranded wire.)
  • 0 AWG (1-2 feet) - Optional. Used from battery to ANL fuse block.
  • 4 AWG (10-20 feet) - Used from battery to Bussmann and/or to and/or from the ANL fuse block
  • 10 AWG (100 feet) - Biggest wire you can reasonably insert into the RFRM. Recommended for fuse to relay connections.
  • 12-22 AWG as needed. Use common sense with ampacities.
  • 0 AWG Ring terminal (QTY 1). Buy correct diameter hole for your battery post.
  • 4 AWG ring terminals (QTY 2). Buy correct diameter hole for your RTMR/RFRM posts.
  • Dual Mini ANL Fuse Block (QTY 1): NVX XFDBU2
  • 125 Amp Mini ANL Fuses (QTY 2) (Change amperage as needed)
 
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The shuggs said:
What's the hype about it being waterproof when the existing PDC isn't. "I don't care that my starter circuit shorted, cuz I can still use my lightbar."
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The Bussmann isn’t designed for immersion, nor is the PDC. The idea with the Bussmann is it has the same or better level of water resistance as the PDC. If you’re driving through puddles of water or mud at speed, the PDC and Bussmann will get splashed. And if you do accidentally get water over the hood, that is one less problem you have to worry about. (Certainly wouldn’t be the worst issue.)

Also, it’s good to have that protection, especially if you hook up circuits that affect safety of the vehicle and passengers. For example, a splash could take out an unprotected power feed for a trailer brake controller, which could have significant negative consequences for safety. But if the Bussmann were to be splashed, the brake circuit would not be affected.

Or what if your e-lockers suddenly died while driving through a mud pit or river crossing? You might end up stuck in a precarious position.
 
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Steel City 06 said:
The Bussmann isn’t designed for immersion, nor is the PDC. The idea with the Bussmann is it has the same or better level of water resistance as the PDC. If you’re driving through puddles of water or mud at speed, the PDC and Bussmann will get splashed. And if you do accidentally get water over the hood, that is one less problem you have to worry about. (Certainly wouldn’t be the worst issue.)

Also, it’s good to have that protection, especially if you hook up circuits that affect safety of the vehicle and passengers. For example, a splash could take out an unprotected power feed for a trailer brake controller, which could have significant negative consequences for safety. But if the Bussmann were to be splashed, the brake circuit would not be affected.

Or what if your e-lockers suddenly died while driving through a mud pit or river crossing? You might end up stuck in a precarious position.
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Just busting your balls.

Well partially. While I agree that having the extra protection from water is useful, I notice that every time auxiliary fuse-boxes come up, no one mentions improving the PDC. The PDC does cover several circuits that are just as important as the ones you mentioned. The PDC has decent protection from splashing, but nothing at the level of the seals/plugs for the wire holes on the Bussmann.
 
The shuggs said:
Just busting your balls.

Well partially. While I agree that having the extra protection from water is useful, I notice that every time auxiliary fuse-boxes come up, no one mentions improving the PDC. The PDC does cover several circuits that are just as important as the ones you mentioned. The PDC has decent protection from splashing, but nothing at the level of the seals/plugs for the wire holes on the Bussmann.
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Understood.

If you really needed immersion protection for the PDC, you would already be doing a lot of other projects. Like snorkels, waterproofing every connector, etc.
 
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One advantage of having the Metri-Pack 280 Series connectors on hand is that they can also be used to construct wiring harnesses from scratch anywhere from 1 connection up to 62 connections in one harness. Here is a dual connection harness:

20200912_150909.jpg
 
Added four additional circuits to the Bussmann RFRM the past few days.
  • Toad Charge (30 amp fused)
  • Trailer Charge (30 amp fused and relay)
  • Vacuum pump (25 amp fused and relay)
  • Toad braking (10 amp fused)
I will also be adding a power line for a trailer brake controller as well. I'm in the process of installing a 7-way RV plug in the front for flat towing plus a 7-way RV socket in the rear for towing. The way it is set up, it could be used for triple towing, but I have no intention of testing that.
20210624_180014.jpg


Also, it seems having the ability to make OEM-grade waterproof wiring harnesses in mere minutes is a lot more useful than I thought. Somehow I've already burned through 100+ female terminals...
20210624_175918.jpg
 
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Steel City 06 said:
View attachment 82105
Underside of the RFRM. The green rubber pieces are removable cavity plugs to prevent water from getting into open holes. Note that every wire is sealed with a cable seal. The terminal post caps are missing in these photos.

(Unfortunately, I'm not the neatest person when it comes to cable management.)
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Thanks for this write-up. I'm trying to get my mind around how these aux panels work. Seems that cheaper ones like this require that each fuse or relay have its own power run from the battery, resulting in lots of individual power lines. But nicer panels like this one have some kind of internal bus bar that uses a single power line from the battery, and then each fuse or relay draws its power from that bus bar. Correct?
 
SSTJ - that's correct. I followed this thread and installed the RFRM in my LJ. The RFRM actually has two separate bus bars. All fuses on one side are powered by one bus bar, and all fuses on the other side are powered by the other bus bar. You can then run from the other side of the fuses (non-bus side) to your loads or to the relays in the center.
 
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You can actually buy the Bussmann RTMR and RFRMs in a number of bussing configurations, usually either 0, 1, or 2 bus bars. I think there might actually be a version of the RTMR that grounds the relays via a ground bus.

(Hence why matching the part number on the model is so important.)
 
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You're right (again). Here's the part numbering system from the RFRM data sheet:

1652795858679.png


The fifth digit signifies the bus setup. Not sure about the RTMR, though - I didn't consider using that one, so didn't grab the data sheet.
 
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Steel City 06 said:
Bussmann base:
The base RTMR or RFRM for your project. I chose the larger RFRM. All the quantities past this section assume you buy an RFRM. Adjust as needed for an RTMR.
Click to expand...
Also, just a note to add. The brackets listed above did not work with the RFRM. They are for the RTMR only, as far as I could tell. If anyone wants a set, let me know, and assuming I can find them (my shop is a mess because I moved everything out and back in to insulate it a few weeks ago), I'll drop them in the mail, free of charge, assuming you are an established member (meaning you've been here before I posted this, have the posts to PM and trade, and didn't Google this and now want it without having contributed to the forum).
 
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sab said:
Also, just a note to add. The brackets listed above did not work with the RFRM. They are for the RTMR only, as far as I could tell. If anyone wants a set, let me know, and assuming I can find them (my shop is a mess because I moved everything out and back in to insulate it a few weeks ago), I'll drop them in the mail, free of charge, assuming you are an established member (meaning you've been here before I posted this, have the posts to PM and trade, and didn't Google this and now want it without having contributed to the forum).
Click to expand...

Very kind of you. I think I'm about to order an RTMR, so I might take you up on the offer. Will send a PM when I'm sure.
 
sab said:
Also, just a note to add. The brackets listed above did not work with the RFRM. They are for the RTMR only, as far as I could tell. If anyone wants a set, let me know, and assuming I can find them (my shop is a mess because I moved everything out and back in to insulate it a few weeks ago), I'll drop them in the mail, free of charge, assuming you are an established member (meaning you've been here before I posted this, have the posts to PM and trade, and didn't Google this and now want it without having contributed to the forum).
Click to expand...
Thanks for noting that. I jury rigged brackets for my RFRM, so I never tested those ones myself.

Planning to print some new brackets out of Lexan at some point.
 
Supply chain update: I had a very hard time finding SPDT relays for this modification. I back-ordered some Song Chuan relays from Mouser on 8/1/21. After a month of waiting, I ordered some SPST relays because I really didn't need the double throw. I just wanted that option, and I wanted them all the same so that spares can be scavenged from non-critical circuits. In the meantime, I kept the order open and once a month I'd get an email asking if I'd like to cancel the order (I didn't). Just this evening, almost 11 months after the order date, Mouser shipped them, and held the price! They doubled in price since I ordered them!

If you've been looking for SPDT relays for this mod, act quick - they only have a few hundred left:

https://www.mouser.com/ProductDetai...sWHSDA/b3tg==&countrycode=US&currencycode=USD
 
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